1. Field of the Invention
This invention relates to a phosphate-free detergent composition having a reduced tendency towards fabric incrustation, and more particularly, to such a composition containing a combination of an aminoalkane polyphosphonate, a polymeric carboxylic acid, and a hydroxyalkane diphosphonate.
2. Discussion of Related Art
Phosphate-free detergents containing finely crystalline aluminosilicates as a phosphate substitute, sodium carbonate or sodium silicates as washing alkali, and polyanionic compounds from the class of aminoalkane polyphosphonic acids and homo- or copolymer polycarboxylic acids derived from acrylic acid, methacrylic, maleic acid and olefinically unsaturated, copolymerizable compounds are known. The phosphonic acids or salts thereof which are used preferably include ethylenediamine tetramethylene phosphonate, generally in the form of their sodium salts. Preferred polymeric carboxylic acids include copolymers of maleic acid with vinylmethylethers and, in particular, copolymers of maleic acid with acrylic acid in a ratio of 1:5 to 1:1 having a molecular weight of from 10,000 to 150,000. These polyacids are also normally present in the detergents as sodium salts. The quantities of aminoalkane phosphonates used are normally 0.1 to 1% by weight and the quantities of copolymers 3 to 6% by weight, based on the detergents. However, the complexing and precipitation-retarding properties (so-called threshold effect) of these additives are generally not good enough to limit the formation of fiber incrustations to the required extent because it has been found that the incrustations increase considerably when the fabrics are repeatedly washed with hard water, and can ultimately assume undesirable proportions. This increase in the incrustations is reflected in increasing hardening and discoloration (graying) of the fabric and may be quantitatively evaluated by determination of the fabric ash.
Accordingly, there exists the problem of reducing this tendency to form such incrustations.